Delight sounds similar to what game designers call "juice" and, done well, it really does make a game feel delightful beyond its pure gameplay.

I've had the same feeling with more utilitarian interfaces, but it's pretty rare. I don't know why. I expect it's partly because we have different expectations for programs than we do for games, partly because the context and the interactions are pretty different, and partly because most organizations do not have the will or the ability to make interfaces that satisfying. (After all, it's the worst sort of thing for most organizations: something that requires taste, time and experience and cannot be managed, measured or executed by committee.)